Unipolar charge sensing using Frisch grid technique for amorphous selenium radiation detectors

We investigate amorphous Selenium Frisch-grid detector design to improve the spectral performance, reliability of single photon detection, and image lag for radiation imaging and detection. Incomplete charge collection due to the low electron mobility in amorphous Selenium results in depth-dependent signal variations. The slow signal rise-time for the portion of the induced charge due to electron-movement towards the anode and significant electron trapping cause ballistic deficit. This phenomenon can be observed from spectrum tailing (also called "electron tailing" for a-Se) and the wide Gaussian spectrum at low photon energies. The implications of this analysis for the design of new Selenium-based photoconductors are discussed, and some preliminary simulation results of the theory are presented.

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